diff --git a/doc/changelog.md b/doc/changelog.md
index 77c32354..fe894aa2 100644
--- a/doc/changelog.md
+++ b/doc/changelog.md
@@ -2,6 +2,10 @@
 
 # Change Log
 
+## Jul-8-2024: Version 3.3.1
+
+- Major refactoring to isolate reciprocal space grid code.
+
 ## Jul-8-2024: Version 3.3.0
 
 - Build system of phono3py was renewed. Now nanobind, cmake, and
diff --git a/doc/conf.py b/doc/conf.py
index ab73c002..b7536d4a 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -60,7 +60,7 @@
 # The short X.Y version.
 version = "3.3"
 # The full version, including alpha/beta/rc tags.
-release = "3.3.0"
+release = "3.3.1"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
diff --git a/phono3py/version.py b/phono3py/version.py
index 87c2d2f1..dcc4a40d 100644
--- a/phono3py/version.py
+++ b/phono3py/version.py
@@ -34,4 +34,4 @@
 # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
-__version__ = "3.3.0"
+__version__ = "3.3.1"